Antagonists create a barrier that blocks endogenous opioid molecules from attaching to opioid receptors. Antagonists attach to opioid receptors, but do not cause the release of dopamine. They are non-addictive and do not lead to physical dependence. VIVITROL blocks opioid receptors in the brain for one month at a time, helping patients to experience fewer heavy-drinking days.


Mechanism of action (MOA) of endorphins


The human brain is stimulated by everything you do. When you do something you enjoy (such as eating delicious food), your brain releases chemicals called endorphins. Endorphins attach to opioid receptors in the brain causing them to release a chemical called dopamine. Dopamine gives you a good feeling to reward you for doing something, which makes you want to repeat these behaviors.

Mechanism of action (MOA) of opioids from alcohol consumption


Endogenous opioids created by alcohol consumption attach to some of the same receptors as endorphins. However, endogenous opioids cause the release of more dopamine than normal enjoyable activities do, causing a “high”. When the high ends, the brain craves this feeling again.

VIVITROL is not right for everyone. There are significant risks from VIVITROL treatment, including risk of opioid overdose, severe reaction at the injection site and sudden opioid withdrawal.
See Important Safety Information below. Discuss all benefits and risks with a healthcare provider. See Prescribing Information and Medication Guide.


  1. VIVITROL [prescribing information]. Waltham, MA: Alkermes, Inc; rev December 2018.
  2. Krupitsky E, Nunes EV, Ling W, Illeperuma A, Gastfriend DR, Silverman BL. Injectable extended-release naltrexone for opioid dependence: a double-blind, placebo-controlled, multicentre randomised trial. Lancet. 2011;377(9776):1506 -1513.
  3. Kosten TR, George TP. The neurobiology of opioid dependence: implications for treatment. Sci Pract Perspect. 2002;1(1):13-20.
  4. Herz A. Endogenous opioid systems and alcohol addiction. Psychopharmacology (Berl). 1997;129(2):99-111.
  5. National Institute on Drug Abuse (NIDA). Drugs, Brains, and Behavior: The Science of Addiction. Bethesda, MD: National Institute on Drug Abuse, National Institutes of Health; 2018. NIH publication 14-5605.
*Eligibility for Alkermes-Sponsored Co-pay Assistance: Offer valid only for prescriptions for FDA-approved indications. You must be at least 18 years old. If you are purchasing your VIVITROL® prescriptions with benefits from Medicare, including Medicare Part D or Medicare Advantage plans; Medicaid, including Medicaid Managed Care or Alternative Benefit Plans (“ABPs”) under the Affordable Care Act; Medigap; Veterans Administration (“VA”); Department of Defense (“DoD”); TriCare®; or any similar state funded programs such as medical or pharmaceutical assistance programs, you are not eligible for this offer. Void where prohibited by law, taxed or restricted. Subject to plan benefit design requirements. Alkermes, Inc. reserves the right to rescind, revoke or amend these offers without notice.